Wood preservation



Patented May 25, 1926.

UNITED STATES ARTHUR H. HOWALD, OF PITTSBURGH, PENNSYLVANIA, ASSIGNOR'TO THE GRASSELLI CHEMICAL COMPANY, OF CLEVELAND, OHIO, A CORPORATION OF OHIO.

woon PRESERVATION.

No Drawing.

This invention relates to the preservation of wood by the impregnation thereof with emulsions of aqueous 1 wood preserving agents in oily wood preserving agents.

As is known, wood may be preserved, that. is, protected against the destructive action of fungi and insects, water, fire, etc., by impregnating it with various materials, all of which may be grouped in two main classes, to wit: (1) oily materials such as coal tar creosote, gas tar oil, crude petroleum, shale oil and the like; and (2) materials which are ordinarily applied by impregnation with their aqueous solutions such as the water soluble inorganic salts, for example, zinc chloride, sodium fluoride, mercuric chloride, copper sulfate and the like. I

It is also known that a more complete preserving effect may be produced by impregnating the wood with materials of both classes. This has been done byimpregnating the wood successively with materials of the two classes, and it has also been proposed to accomplish the impregnation of the wood with the two classes, of materials simultaneously by the use of emulsions of oily preserving agents in aqueous preservmg agents.

The present invention as distinguished from the prior processes referred to relates to the impregnation of wood with emulsions of aqueous preserving agents in oily preserving agents. In order that the distinction may be clearly understood, it is stated that there are two general types of emulsions of oily and aqueous liquids, the one in which the aqueous liquid constitutes the continuous phase of the emulsion and as a rule is the predominating ingredient, and the other in which the oily liquid constitutes the continuous phase and the aqueous liquid is in the disperse phase. The impregnating emulsions to which the present invention relates are of the second type, whereas the emulsions referred to as having been pro posed heretofore for wood impregnation are of the first type.

An emulsion for the impregnation of wood must possess certain characteristics, the more important of which are the following:

The emulsion must be sufiiciently permanent so that it may be handled in the impregnating bath without stratifying into Application filed January 23, 1924. Serial No. 688,098.

layers of the individual components. The ingredients of the emulsion must be in such proportion as to give the desired quantity of each preserving agent in the impreg nated wood. The emulsion must of course possess sufficient fluidity and penetrating properties to enable it to penetrate well into the wood. In the course of a careful study of the impregnation of Wood with emulsions of oily and aqueous preserving agent s I have observed a marked tendency toward uneven impregnation by the two agents, that is, the proportions of the preserving agents found in the impregnated wood are not the same as the proportions of the agents in the impregnating bath. This result may be explained upon the supposition that the subdivision of the disperse phase in the emulsion used was insufficient to permit the particles thereof to penetrate into the wood along with the continuous phase, and as a result the disperse phase was filtered out. I have therefore added as a further essential characteristic of wood impregnating emulsions the requirement that the emulsificati'on be sufficiently thorough and the disperse phase sufliciently finely divided to pass freely through the pores of the wood along with the continuous phase.

Emulsions of aqueous preserving agents in oily preserving agents prepared in accordance with my invention meet with all of the mentioned requirements.

The invention is illustrated in the following specific examples:

An emulsion is prepared by mixing 15 parts of a 17.5% aqueous zinc chloride solution with parts of asphaltic petroleum residue and parts of asphaltic base crude oil. The mixture may be emulsified in any suitable manner, but preferably in accord ance with my invention it is subjected to what may for the purpose of identification be called super-emulsification or homogenization. This method of emulsification consists in passing the mixture preferably ,at an elevated temperature of say C. and under a pressure 'of from 1000 to 3000 pounds but preferably. in the neighborhood of 2000 pounds per square inch, throughan emulsifying valve of the well known type consisting of a conical valve seat and a com-- cal plug pressed against theconical seat by a strong spring. The resulting emulsion is used for the impregnation of wood in aceordance with any of the known and approved methods. For instance, the wood to be impregnated may simply be soaked in the emulsion, but it is preferred to accelerate the impregnation by one or more of the usual expedients involving heating, steaming, evacuation, application of pressure, etc. A suitable procedure is to place the wood in a closed vessel and steam it with live steam at sa 20 to 40 pounds pressure, then evacuate t e vessel and run in the emulsion, then apply pressure to the contents of the vessel to drive the emulsion into the pores of the wood, then draw off the unabsorbed liquid and again evacuate the vessel. This is a well known procedure for the impregnation of wood with preserving liquids and may be modified or substituted wlthout departure from my invention.

1 A great variety of combinations of the two classes of preservative materials may be used. As is stated, the invention consists genera'll in the use for the impregnation of wood 0 emulsions of aqueous reserving agents in oily preserving materia There are numerous agents of each class from which may be selected numerous combinations, the selection of course logically depending upon the kind of preservation desired, the cost of the materials and perhaps also other factors. The invention is not limited to the use of emulsions containin a single material of each class but inclu es the use of emulsions of combinations of both classes of materials, for instance, an emulsion may be prepared containing a water so lution oftwo or more water soluble salts and two or more oily materials.

In the preparation of the .emulsions there may be used an emulsifying or stabilizing agent such as, for instance, asphalt, stearine pitch rosin, soaps and the like. A constituent oi the oily part of the emulsion may serve as the emulsifying or stabilizing agent as is the case in the foregoin example in which the asphaltic content of the asphaltic base crude oil serves this purpose.

The emulsions of aqueous preserving agents in oily preserving agents possess certain advantages over emulsions of oily preserving (igents in aqueous preserving agents for we impregnation and preservation. In the impregnation of wood such as railroad cross ties it is usually desired to introduce into the wood a relatively greater quantity of the oily agent than of the aqueous agent, which cannot be done when the aqueous agent constitutes the predominating proportion of the emulsion and the impregnatlon is even. But with an emulsion-of the aqueous agent in an oily agent in which I the oily agent constitutes the bulk and the impregnation is even, the desired ratio of the two agents in the impregnated wood may makes possib be obtained. Moreover, the use of emulsions of the aqueous agents in the oily agents e the use of inexpensive oils and oils which, like asphaltic base crude oils, tars, and the like, cannot be emulsified into water or aqueous salt solutions but into which a sufiicient quantity of aqueous solutions of preserving salts may be readily emulsified.

The emulsions are stable and uniform and possess desirable penetrating properties. As as been stated, they ermit the even impregnation of the woo with the two t pes of preservative materials. This has en proven in numerous tests by chemical and physical examination of impregnated wood. An indication that the impregnation of the wood is even is that the bleedings therefrom have substantially the same composition as the emulsion used for the impregnation.

The impregnated wood has its fibers coated and its pores filled with a uniform mixture of the two types of impregnating agents.

I claim 1. Process of preserving wood which comprises impregnating the same with a superemulsified mixture of an aqueous preserving agent in an oily preserving agent. 05

2. Process of preserving wood which comprises impregnating the same with a superemulsified mixture of an aqueous preserv ing agent and an oily preserving agent containing a predominating proportion of the oily preservin agent.

3. Processo preserving wood which comprises impregnating the same with a superemulsified mixture of an aqueous solution of a preservative salt in an oily preservative agent a 4. Process of preserving wood which comprises im regnating the same with a superemulsifie mixture of an asphaltic or pitch bearing oil and an-aqueous solution of zinc chloride in which the aqueous solution of zinc chloride constitutes the disperse phase.

5. Process of preserving wood which comprises impre ating the same with a homogenized emulsion of an aqueous solution of a wood preset-vin inorganic material and an asphaltic petroleum oil containing a predominating proportion of the asphaltic petroleum oil.

6. A fluid for the impregnation of wood consistin of an emulsion of an aqueous solution o? a preserving substance or substances in an oil, the disperse phase of said emulsion being in a sufficiently fine state of subdivision to penetrate into the wood, said emulsion being substantially free of emulsified material.

7. Process of preserving wood which coin-' prises impregnating .same with an emulsionof about 15 parts of an aqueous solution of l zinc chloride in about 85 parts of an assuper-emulsified mixture of an aqueous pre- 10 phaltic oil. servin agent in an oily preserving agent.

8. Process of preservlng Wood which com- 10. is a new product wood impregnated prises impregnating same with an emulsion with a super-emulsified mixture containing of about 15 parts of a 17.5% solution of zinc a dispersion of an aqueous preserving agent chloride with a mixture of about 30 parts of in an oily preserving agent. 15 asphaltie petroleum residue and about 55 In testimony whereof, I aflix my signaparts of asphaltic base crude oil. ture.

9. As a new wood impregnating agent a ARTHUR M. HOWALD. 

